CHARACTERIZATION, ANALYSIS, AND TESTING Flashcards

1
Q

analytical branch of polymer science

A

➢Polymer characterization

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2
Q

➢Polymer characterization is a technique used to determine the

A

molecular properties, structure, and behavior of polymers.

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3
Q

The information obtained from polymer characterization can also be
used for

A

process control and product quality assessment

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4
Q

Characterization techniques are typically used to
determine

A

molecular mass
molecular structure
morphology
thermal properties
mechanical properties

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5
Q

Extremely large molecular weights are observed in polymers with

A

very long chains

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6
Q

The molecular mass of a polymer _______ from typical molecules

A

differs

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7
Q

t polymerization reactions produce a _________ of molecular
weights and shapes.

A

distribution

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8
Q

During the polymerization process, ______ polymer chains will grow to
the same length

A

not all

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9
Q

resulted in the different lengths in the growing part of the polymerization

A

distribution of chain lengths or
molecular weights.

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10
Q

The distribution of molecular masses can be summarized by

A

number average molecular weight
weight average molecular weight
polydispersity.

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11
Q

common methods for determining number average molecular weight,
weight average molecular weight and
polydispersity
parameters

A

colligative property measurements
static light
scattering techniques
viscometry
size exclusion chromatography

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12
Q

There are four molecular weight
averages in common use

A

number-average molecular weight, Mn
the weight-average molecular weight, Mw
the z-average molecular weight, Mz
viscosity-average molecular weight, Mv

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13
Q

highest to lowest

A

Mn < Mv < Mw < Mz

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14
Q

equation for Number-Average Molecular Weight, Mn

A

(image 5 & 6)

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15
Q

Determination of
Molecular Weight (physical and chemical methods)

A
  1. end group analysis
  2. measurement of colligative properties
  3. light scattering
  4. Ultracentrifugation
  5. dilute solution viscosity
  6. gel permeation chromatography (GPC).
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16
Q

equation of Number-Average Degree of Polymerization, DPn

A

(image 7)

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17
Q

equation of Weight-Average Molecular Weight

A

(image 8 &9)

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18
Q

if all species in a polymer sample have the same molecular weight

A

𝑀𝑛 = 𝑀𝑤 = 𝑀z

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19
Q

If all species in a polymer sample have the same molecular weight (that
is, the polymer is ____________)

A

monodisperse

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20
Q

ratio Mw/Mn

A

polydispersity index (PDI)

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21
Q

as a simple measure of the polydispersity of the polymer sample

A

polydispersity index (PDI)

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22
Q

a chemical method use for calculating the number-average molecular weight of polymer samples whose molecules contain reactive functional groups at one end or both ends of the molecule.

A
  1. End-group Analysis
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23
Q

This method is limited to the determination of polymers with a molecular weight of less than about 20,000.

A
  1. End-group Analysis
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24
Q

method of analysis in an end-group Analysis

A

✓Titrimetric method
✓Nuclear magnetic resonance (NMR)
✓mass spectrometry
✓vibrational spectrometry, like infrared and raman spectroscopy.

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25
Limitations/Disadvantages End-group Analysis
- not applicable to polymers that lack reactive or easily detectable end-groups. ➢not be suitable for polymers with very high molecular weights. ➢problem of selecting a suitable solvent to dissolve the polymer
26
Properties of solutions that depend on the number of molecules present and not on the kind of molecules
colligative properties
27
properties included in colligative properties
boiling point elevation, freezing point depression, and osmotic pressure.
28
steps in colligative present
1.beginning with a known mass of solute 2. know the total number of molecules in solution, - used the knowledge of any of these colligative properties 3. allows computation of the number-average molecular weight.
29
Colligative Properties device for Boiling Point Elevation
Ebulliometry
30
Ebulliometry (Boiling Point Elevation) simple mechanism
boiling point of a solution of known concentration vs (compared) solvent at the same pressure.
31
Boiling point of the solution is _______ than the pure solvent
higher
32
Boiling point elevation phenomenon is used to determine the
molecular weight of polymers
33
Colligative Properties device for Freezing Point Depression
Cryoscopy
34
Calculation of the freezing point depression
calculate freezing-point depression of the solvent get molecular weight of the solute exactly the same way as for the boiling-point elevation
35
freezing point depression (mechanism)
- analyzing the melting behavior of a substance as it is frozen. - By measuring the time it takes for a specific substance to melt at a certain temperature - its molecular weight can be calculated.
36
Like ebulliometry, this is also limited to relatively low-molecular-weight polymers with Mn up to ______________
Cryoscopy , 50,000
37
most important among all colligative properties for the determination of molecular weights of synthetic polymers.
Osmotic pressure
38
is a technique for the determination of molecular masses of polymers by means of osmosis.
Membrane osmometry
39
describes the attempt of solvent molecules to go through a semipermeable membrane into a solution.
The phenomenon of osmosis
40
Membrane osmometry is useful to determine Mn about __________________ and less than __________
20,000-30,000 g/mol and less than 500,000 g/mol
41
Limitations/Disadvantages of ebulliometry
- time consuming - sensitive to changes in the atmospheric pressure - not suitable for use with volatile substances or highly reactive chemicals due to the risk of explosion.
42
Limitations/Disadvantages of ebulliometry
time-consuming (requires a sudden freezing and slow thawing process. - sensitive to impurities in the monomer solutions (defective polymer formation)
43
Limitations/Disadvantages of the use of boiling point increase and freezing point lowering is
limited to the determination of the molecular weights of relatively small polymers
44
Limitations/Disadvantages of membrane osmometry
- simple but takes hours to few days in diffusion of solvent through the semipermeable membrane. - very slow process and the time taken to attain equilibrium is extremely high. -useful in the molecular weight range of 30,000 to 1,000,00
45
important technique for the determination of weight-average molecular weight, Mw
Light- Scattering Method
46
absolute method of molecular weight measurement.
Light- Scattering Method
47
LightScattering Method can furnish information about
- size and shape of polymer molecules in solution - parameters that characterize the interaction between solvent and polymer molecules
48
When polarizable particles are placed in the __________________ of a beam of light, the light scattering occurs.
oscillating electric field
49
Light scattering method depends on the ____
light
50
when light is passing through polymer solution, it is measured by _________
lose energy
51
lose energy happened in Light-Scattering Method due to the
absorption, conversion to heat and scattering
52
The intensity of scattered light relies on the ________________ that is proportionality constant which depends on the molecular weight
concentration, size and polarizability
53
a technique that measures the intensity of the scattered light to obtain the average molecular weight Mw of a macromolecule like a polymer or a protein in solution
Static light scattering
54
a coherent laser beam is used to analyze a sample
Static light scattering measurement
55
The laser beam is ________________ the sample
directed through or passes through
56
The scattering intensity of the laser beam is measured at a fixed angle, which is
90°
57
Light-Scattering Method limitations and disadvantages
- non-selective and thus requires purified extracts without co-eluting contaminants to generate useful data. - Requires a solvent with a different refractive index compared to the solute ✓sensitive to high-molecular-weight species/dust/aggregates. - high price and requires difficult clarification of the solutions
58
Light-Scattering Method advantages
it provides information about macromolecules without any calibration with polymer standards.
59
defined as the measure of the opposing force of material to flow
Viscosity
60
used to measure viscosity
Viscometry
61
The average molecular weight that is measured in viscometry is the
viscosity average molecular weight Mv
62
The dependence of viscosity on ______ permits estimation of an average molecular weight from solution viscosity.
size
63
equation gives the relationship between viscosity and average molecular weight
Mark-Houwink
64
Mark-Houwink equation
image 26
65
most common type of viscometer that is used for the determination of viscosity of polymer solution.
Ubbelohde viscometer
66
Ubbelohde viscometer mechanism
1. A liquid is introduced into the reservoir 2. sucked through the capillary and measuring bulb. 3. The liquid is allowed to travel back through the measuring bulb 4. the time it takes for the liquid to pass through two calibrated marks (start and stop marks) is a measure for viscosity.
67
Viscometry ➢Limitations/Disadvantages
- limited to measuring materials in the liquid or semi-liquid state, (not applicable to all polymers) -Viscometry can be affected by the presence of other substances in the sample (solvents or additives) - more concentrated a polymer solution, the more large molecules you have exerting drag
68
The more concentrated a polymer solution,___________________________
the more large molecules you have exerting drag and interacting with each other.
69
Higher concentration leads to a _________________
higher viscosity measurement
70
extremely powerful method for determining the complete molecular weight distribution and average molecular weights
Gel permeation chromatography (GPC)
71
essentially a process for the separation of polymer molecules according to their size.
Gel permeation chromatography (GPC)
72
Gel permeation chromatography (GPC) MECHANISM
- dilute polymer solution is injected into a solvent stream - passes through a column packed with porous gel particles
73
porosity of porous gel particles
range 50^-10^6 A
74
known as gel filtration gel exclusion chromatography size-exclusion chromatography (SEC), molecular sieve chromatography
Gel permeation chromatography (GPC)
75
Gel permeation chromatography (GPC) limitations
- limited number of peaks that can be resolved within the short time scale of the run. - requires around at least a 10% difference in molecular weight for a reasonable resolution of peaks to occur. - Filtrations must be performed before using the instrument to prevent dust and other particulates from ruining the columns and interfering with the detectors. - The molecular masses of most of the chains will be too close for the GPC separation to show anything more than broad peaks.
76
used to purify and characterize low-molecular-weight polymers.
Ultracentrifugation
77
In ______________, both Mw and Mz may be determined by subjecting dilute solutions of polymers in appropriate solvents to ______________ at high speeds
Ultracentrifugation, ultracentrifugal forces
78
Solvents with densities and indices of refraction ___________ from the polymers are chosen to ensure polymer motion and optical detection of this motion.
different
79
The ultracentrifuge is operated at __________ speeds up to ____________ in order to transport the denser polymer molecules through the less dense solvent to the cell bottom
extremely high , 70,000 rpm
80
Mw and Mz formula for Ultracentrifugation
(image 31)
81
Limitations of Ultracentrifugation
Low sample yield time-consuming process extremely expensive devices
82
In preparative ultracentrifugation, samples must be ___________ several times after spinning, to ensure that there is no cross-contamination between fractions.
washed
83
Samples for preparative centrifugation are usually ______________ (e.g., tissues) or _______________ (e.g., cell suspensions or blood).
limited in size , volume
84
In every wash step that a sample is subjected to, there is a ___________ , and thus, after an ultracentrifugation protocol, the yield can be very low.
loss of material
85
has proved to be a rapid and precise method of molecular-weight determination, often requiring as little as a half hour per sample.
gel permeation chromatography , GPC
86
two techniques that are encountered most commonly are
intrinsic viscosity and gel permeation chromatography , GPC
87
Many of the analytical techniques used to determine the ____________________________________ are also used in** polymer characterization**.
molecular structure of unknown organic compounds
88
_________________________ such as ultraviolet-visible spectroscopy, infrared spectroscopy, Raman spectroscopy, nuclear magnetic resonance spectroscopy, electron spin resonance spectroscopy, X-ray diffraction, and mass spectrometry are used to identify common functional groups.
Spectroscopic techniques
89
Spectroscopic techniques such as ultraviolet-visible spectroscopy, infrared spectroscopy, Raman spectroscopy, nuclear magnetic resonance spectroscopy, electron spin resonance spectroscopy, X-ray diffraction, and mass spectrometry are used to identify common ______________
functional groups.
90
microscale property that is largely dictated by the** amorphous or crystalline portions ** of the polymer chains and their influence on each other
Polymer morphology
91
are especially useful in determining these microscale properties, as the domains **created by the polymer morphology are large enough** to be viewed using modern microscopy instruments.
Microscopy techniques
92
➢Some of the most common microscopy techniques used are
X-ray diffraction Transmission Electron Microscopy Scanning Transmission Electron Microscopy Scanning Electron Microscopy Atomic Force Microscopy
93
ANALYSIS AND TESTING
A. CHEMICAL ANALYSIS OF POLYMERS B. SPECTROSCOPIC METHODS C. X-RAY DIFFRACTION ANALYSIS D. MICROSCOPY E. THERMAL ANALYSIS F. PHYSICAL TESTING
94
MECHANICAL PROPERTIES
a. Stress-Strain Properties in Tension b. Fatigue Tests c. Impact Tests d. Tear Resistance e. Hardness f. Abrasion Resistance
95
THERMAL PROPERTIES
a. Softening Temperature b. Flammability
96
OPTICAL PROPERTIES
a. Transmittance and Reflectance b. Color c. Gloss d. Haze e. Transparency
97
ELECTRICAL PROPERTIES
a. Resistivity b. Dielectric Constant c. Dielectric Strength d. Arc Resistance
98
CHEMICAL PROPERTIES
a. Resistance to Solvents b. Vapor Permeability c. Weathering
99
polymer is allowed to react to **form low-molecular-weight fragments** that are condensed at liquid-air temperature
Mass Spectrometry
100
volatilized, ionized and separated according to mass and charge by the action of electric and magnetic fields
Mass Spectrometry
101
Mass spectrometry, from the abundance of the various ________found, the ________________ of the low molecular weight species can be inferred.
ionic species, structures
102
example of Mass Spectrometry
Matrix-Assisted Laser Desorption/Ionization (MALDI)
103
is an **ionization technique** that uses a **laser energy-absorbing matrix **to create ions from large molecules with minimal fragmentation
matrix-assisted laser desorption/ionization (MALDI)
104
can be used to determine the molar mass distribution
matrix-assisted laser desorption/ionization (MALDI)
105
Mass Spectrometry Strength
1.**Compound Identification** -accurate based on their mass spectra, allowing the detection of unknown or trace compounds. 2.**High Sensitivity and Specificity **-enabling detection of compounds at very low concentrations, and high specificity due to the unique mass spectra of different compounds. 3.**Quantitative Analysis**-accurate quantification of compounds based on ion abundance
106
Mass Spectrometry Limitations
1.**Sample Preparation:** Samples must be compatible with the ionization method 2.**Complexity and Cost**: Mass spectrometers expensive to purchase, maintain, and operate. Specialized expertise is required for method development and data interpretation. 3.**Instrument Sensitivity:** presence of contaminants or interfering compounds
107
method of separation in which gaseous or vaporized components are distributed between a moving gas phase and fixed liquid phase or solid adsorbent
Gas Chromatography
108
Gas Chromatography step by step
- adsorption, separation is achieved. - components are detected as they emerge from the chromatographic column - From the detector signal, **number, nature, and amounts of the components** present.
109
analytical technique used **to separate the chemical components** of a sample mixture and then **detect** them to determine their presence or absence.
Gas Chromatography
110
It is also used to figure out** how much is present** in the sample.
Gas Chromatography
111
analytical method that combines the features of **gas-chromatography and mass spectrometry** to identify different substances within a test sample.
Gas chromatography– mass spectrometry
112
combines the separation capabilities of gas chromatography with the identification and quantification abilities of mass spectrometry
Gas chromatography– mass spectrometry
113
can provide detailed information about the molecular structure and composition of polymers, including their **monomer sites, stereochemistry, and branching patterns**.
Gas chromatography– mass spectrometry
114
Gas Chromatography Strengths
**1. High Separation Efficiency**: Allows the separation of complex mixtures into individual components, even for compounds present in trace amounts. **2. Quantitative Analysis**: Provides accurate quantification of compounds through calibration curves or peak area integration in the chromatogram. **3. Wide Range of Applications**: Applicable to a diverse range of sample types and compounds, offering versatility in analytical tasks
115
Gas Chromatography Limitations
**1. Limited Volatility**: Compounds need to be volatile or semi-volatile to be efficiently separated and detected by GC. **2. Thermal Stability**: Some compounds may decompose or react within the high-temperature environment of the GC column, affecting their separation and detection. **3. Sample Preparation**: Sample preparation steps, such as extraction and derivatization, might be required, adding complexity to the analysis
116
analysis of infrared light interacting with a molecule
Infrared Spectroscopy
117
can be analyzed in three ways by measuring absorption, emission and reflection.
Infrared Spectroscopy
118
ways to measure Infrared Spectroscopy
absorption, emission and reflection.
119
measures the vibrations of atoms
Infrared Spectroscopy
120
to determine the functional groups
measures the vibrations of atoms
121
**non-destructive analytical technique** that measures the** absorption or transmission **of infrared radiation by a sample as a function of **frequency or wavelength**
Fourier transform infrared spectroscopy (FTIR)
122
reliable and cost-effective analytical tool for identification of polymers and assessment of the quality of plastic materials
Fourier transform infrared spectroscopy (FTIR)
123
In Fourier transform infrared spectroscopy (FTIR), when a plastic material absorbs **infrared light,** typically in the mid-infrared region, the resulting s**pectrum (absorbance or transmittance)** gives a distinctive _____________ that can be used to easily screen and test samples for many different applications.
“fingerprint”
124
Fourier transform infrared spectroscopy (FTIR) Strengths
◦ **high sensitivity, specificity, and ability** to provide a wealth of information about the chemical **composition and structure** ◦ can **detect very small amounts** in complex mixtures and can provide **quantitative data**. ◦ relatively **simple and rapid technique** that can analyze solid, liquid, and gas samples.
125
Fourier transform infrared spectroscopy (FTIR) Limitations
- inability to provide **three-dimensional structure** of a molecule and its **sensitivity **to interference from water and other atmospheric gases. ◦ pone to interference from sample preparation artifacts, such as **impurities or contaminants. ** ◦ **expensive technique **that requires specialized training and expertise to interpret the spectra correctly.
126
powerful analytical technique used to study the **molecular structure, dynamics, and composition of organic and inorganic ** compounds
Nuclear Magnetic Resonance (NMR) spectroscopy
127
Nuclear Magnetic Resonance (NMR) spectroscopy Strengths
**Structural Information**: detailed molecular structures, including bond connectivity, stereochemistry, and molecular dynamics. **Non-Destructive and Non-Invasive:** allows repeated measurements without altering the sample. **Quantitative Analysis:** quantifying the abundance of different nuclei within a sample. **Versatility:** wide range of compounds, including organic and inorganic molecules, solids, liquids, and gases.
128
It exploits the **magnetic properties** of certain atomic nuclei **within a magnetic field** to provide detailed information about the chemical environment of atoms in a molecule
Nuclear Magnetic Resonance (NMR) spectroscopy
129
In Nuclear Magnetic Resonance (NMR) spectroscopy, _________ with an odd number of protons or neutrons possess a _____________ and a magnetic moment, which allows them to absorb and emit electromagnetic radiation at specific frequencies
Atomic nuclei , nuclear spin
130
Nuclear Magnetic Resonance (NMR) spectroscopy Limitation
**Sensitivity**: limited in sensitivity, requiring large sample and limits trace analysis. **Instrument Cost and Complexity**: expensive to purchase and maintain **Sample Requirements**: Samples must be pure and relatively concentrated, and sample preparation can be timeconsuming. **Complex Spectral Interpretation**: Interpreting NMR spectra might be challenging, especially for complex molecules
131
detection of free radicals
Electron Paramagnetic Resonance Spectroscopy
132
uniquely characterized by their **magnetic moment**, arising from the presence of an **unpaired electron**.
free radicals
133
EPR works by measuring the presence of __________ or molecules with unpaired electrons, and by observing the____________ of microwaves within a static magnetic field.
paramagnetic ions , resonant absorption
134
can be used to study radical reactions in polymers
Electron Paramagnetic Resonance Spectroscopy
135
non-invasive and non-destructive magnetic resonance technique, therefore perfect for detecting **paramagnetic species** like free radicals, bi-radicals, transition metal ions, triplet state systems, and point defects.
Electron Paramagnetic Resonance Spectroscopy
136
Electron Paramagnetic Resonance Spectroscopy Strengths
**◦ Sensitivity to Unpaired Electrons**: making it suitable for studying free radicals and paramagnetic species present in trace amounts. **◦ Non-Destructive and Non-Invasive**: doesn’t require extensive sample preparation, allowing for repeated measurements on the same sample. **◦ Information about Molecular Structure and Environment:** information about the electronic structure, coordination environment, and dynamics of paramagnetic species
137
valuable technique for analyzing polymers, providing insights into their electronic structure, composition, and **molecular interactions**.
Ultraviolet–visible spectroscopy
138
used to study the **absorption of ultraviolet and visible light **by polymer molecules
Ultraviolet–visible spectroscopy
139
Ultraviolet–visible spectroscopy steps
1. light source 2. wavelength selector (inlet: light) 3. sample (inlet: light) 4. detector (inlet: light) 5. computer for singe processing and output (inlet: electric current)
140
Ultraviolet–visible spectroscopy principle
Electronic Transitions
141
Polymers exhibit electronic transitions in the UV and visible regions due to the presence of _____________. These transitions involve movement of electrons between energy levels, leading to absorption of specific wavelengths of light
conjugated double bonds or chromophores
142
Applications of Ultraviolet–visible spectroscopy
Polymer Characterization - functional groups, analyzing the presence of chromophores or additives. Quality Control - purity and composition Polymer Processing - degradation or changes
143
Ultraviolet– visible spectroscopy Strengths
**Qualitative Analysis**: information about the presence of specific functional groups or chromophores within polymers. **Rapid Analysis: **Quick measurements enable efficient screening of samples. **Non-destructive: **Allows for the analysis of polymer samples without altering their structure.
144
Ultraviolet– visible spectroscopy Limitations
**Quantitative Analysis Challenges: **due to the complex nature of polymer mixtures and overlapping absorption bands. **Sensitivity**: Limited sensitivity for trace-level analysis of polymers compared to other techniques. **Sample State**: Limited to solutions or transparent solid forms, which might not represent the polymer’s actual structure in its intended application
145
powerful **qualitative and quantitative tool **with some particular advantages for the analysis of polymers.
Raman spectroscopy
146
an analytical technique used to study molecular vibrations in materials by measuring the scattering of light when it interacts with a sample
Raman spectroscopy
147
provides information about molecular structure, chemical composition, and bonding within a sample based on the vibrational modes of its constituent molecules
Raman spectroscopy
148
Raman spectroscopy Principle:
- a laser beam is directed onto a sample - small fraction of the incident light undergoes inelastic scattering. - The scattered light exhibits **energy shifts** corresponding to the **vibrational energy levels **of the molecules in the sample. - The resulting spectrum provides information **about molecular vibrations,** allowing identification of** functional groups** and chemical bonds present
149
Raman spectroscopy ➢Strengths
**1.Chemical Specificity:** detailed information about chemical composition, including *molecular structures, functional groups, and bonding configurations.*** **2.Non-Destructive and Non-Invasive**: requires minimal to no sample preparation, and it can analyze samples in situ. **3.Versatility: **wide range of materials, including solids, liquids, gases, and biological samples. **4.High Spatial Resolution**: With modern instrumentation, Raman spectroscopy can achieve **high spatial resolution**, enabling microscopic analysis at the sub-micron level.
150
Raman spectroscopy ➢Limitations
**1.Fluorescence Interference**: can interfere with Raman signals, reducing the signal-to-noise ratio and complicating spectral interpretation. 2.Low Sensitivity: requiring longer acquisition times or high laser power for some samples, which might cause sample damage. **3.Water and Background Interference:** Water and other background signals may overlap with Raman bands, affecting accuracy in aqueous or complex samples. **4.Instrumentation Complexity and Cost:** Highperformance Raman spectrometers can be expensive, and interpreting complex spectra may require expertise
151
nondestructive technique that provides detailed information about the **crystallographic structure**, chemical composition, and physical properties of a material
X-Ray diffraction analysis (XRD)
152
has become the go-to tool for identifying the type and **crystallinity of polymer** materials
X-ray diffraction (XRD)
153
X-ray diffraction analysis works by passing X-rays through** a sample** and analyzing the ____________ produced by the scattering of X-rays by the polymer molecules.
diffraction pattern
154
X-ray diffraction analysis technique provides information about the _______________________________ of the polymer.
chain length, flexibility, and degree of order
155
X-ray diffraction analysis Strengths
**◦ Least expensive** and most convenient. **◦ Widely used **method to determine crystal structures. ◦ The best method for** phase analysis.** ◦ X-rays are n**ot absorbed very much by air**, so the sample need not be in an evacuated chamber.
156
X-ray diffraction analysis Limitations
X-rays do not interact very strongly with lighter elements
157
category of microscopes that uses visible light to magnify and image small samples.
Light Microscopy
158
valuable for examining the texture of solid opaque polymers
Light Microscopy
159
technique used to observe the orientation of molecules in a sample under a microscope.
Polarized-light Microscopy
160
It is often used with polymers to study their **structure**, as the **orientation of the polymer chains** can reveal information about their molecular organization.
Polarized-light Microscopy
161
is a type of microscopy that uses **interference patterns** produced by the **incoherent light scattered** by specimens to create an image.
Phase-contrast Microscopy
162
commonly used in materials science and polymer science to **observe changes in the morphology **of polymers during **phase transitions or in response to external stimuli**
Phase-contrast Microscopy
163
can provide valuable information about the structure and behavior of polymers at the **micrometer scale**, such as **domain size, chain organization, and interface properties**
Phase-contrast Microscopy
164
powerful tool in the study of the **morphology of crystalline** polymers
Electron Microscopy
165
uses a **beam of electrons** and their **wave-like characteristics** to magnify an object's image, unlike the optical microscope that uses visible light to magnify images
Electron Microscopy
166
a microscope that uses a beam of electrons as a source of illumination
Electron Microscopy
167
Electron Microscopy use _ that are _ to the glass lenses of an optical light microscope** to control the electron beam**, for instance focusing them to produce magnified images or electron diffraction patterns.
electron optics , analogous
168
type of electron microscope that produces images of a sample by** scanning the surface ** with a focused beam of electrons.
Scanning Electron Microscope (SEM)
169
Under this, the electrons interact with atoms in the sample, producing various signals that contain information about the** surface topography ** and composition of the sample
Scanning Electron Microscope (SEM)
170
type of electron microscope that transmits electrons through a** thin sample**, resulting in an image of the **sample's interior structure at the atomic level**
Transmission Electron Microscopy (TEM)
171
analytical technique used to visualize the smallest structures in matter
Transmission Electron Microscopy (TEM)
172
Unlike optical microscopes, which rely on light in the visible spectrum, Transmission Electron Microscopy (TEM) can **reveal stunning detail at the atomic scale** by magnifying nanometer structures up to ______________
50 million times
173
thermoanalytical technique in which the **difference** in the **amount of heat required **to increase the temperature of a **sample and reference** is measured as a function of temperature.
. Differential Scanning Calorimetry
174
used widely for examining polymeric materials to determine their **thermal transitions**. Important thermal transitions include the **glass transition temperature (Tg), crystallization temperature (Tc), and melting temperature (Tm).** The observed thermal transitions can be utilized to compare materials.*
. Differential Scanning Calorimetry
175
the material under study and an **inert reference **are made to undergo** identical thermal cycles**, (i.e., same cooling or heating programme) while recording any **temperature difference between sample and reference**
Differential Thermal Analysis
176
Changes in the sample, either exothermic or endothermic, can be detected relative to the inert reference
Differential Thermal Analysis
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This differential temperature is then plotted against time, or against temperature (DTA curve, or ________________).
thermogram
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Curve that provides data on the transformations that have occurred, such as glass transitions, crystallization, melting and **sublimation**.
DTA curve
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a sensitive balance is used to follow the weight change of the sample as a function of temperature
Thermogravimetric Analysis
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Typical applications include the **assessment of thermal stability **and **decomposition temperature, extent of cure in condensation polymers, composition** and some information on **sequence distribution** in copolymers, and composition of filled polymers, among many others
Thermogravimetric Analysis
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measures the **mechanical response** of a polymer system as the temperature is changed.
Thermomechanical Analysis
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Typical measurements include **dilatometry, penetration or heat deflection, torsion modulus, and stress-strain behavior**
Thermomechanical Analysis
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stress-strain curve showing elastic and plastic region
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One of the most informative mechanical experiments for any material is the determination of its stressstrain curve in tension.
Stress-Strain Properties in Tension
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done by measuring continuously the force developed as the sample is **elongated at constant rate of extension**
Stress-Strain Properties in Tension
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**maximum stress** that a material can withstand while being stretched or pulled before breaking.
Tensile strength
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material property and is the stress corresponding to the yield point at which the material begins to** deform plastically**
Yield strength
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mechanical property of solid materials that measures the **tensile or compressive stiffness** when the force is applied **lengthwise.**
Young's modulus (or Young modulus)
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measure of the stress or force that is applied in a direction **parallel to the surface ** of a material.
Shear stress
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It is typically defined as the **force per unit area** perpendicular to the plane of shearing force.
Shear stress
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refers to the **bending or storage of stress or strain** in a material.
Flexure
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It is a mechanical phenomenon that occurs when force is applied to a flexible material.
Flexure
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In flexure, the amount of bending that occurs depends on the material's properties, such as its ___________ and _______________
modulus of elasticity , cross-sectional area
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is the twisting of an object due to an applied **torque.**
Torsion
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the force that is responsible for the **deformation** of the material such that the **volume of the material reduces**.
Compressive stress
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High compressive stress leads to ____________ of the material due to tension.
failure
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1. soft and weak 2. hard and brittle 3. soft and tough 4. hard and strong 5. hard and tough
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Based on Stress-Strain Curve Soft, weak polymer
modulus: low yield strength: low ultimate strength: low elongation at break: ,moderate
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Based on Stress-Strain Curve Soft, tough polymer
modulus: low yield strength: low ultimate strength: yield stress elongation at break: high
200
Based on Stress-Strain Curve hard, brittle polymer
modulus: high yield strength: none ultimate strength: moderate elongation at break: low
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Based on Stress-Strain Curve hard, strong polymer
modulus: high yield strength: high ultimate strength: high elongation at break: moderate
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Based on Stress-Strain Curve hard, tough polymer
modulus: high yield strength: high ultimate strength: high elongation at break: high
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When subjected to **cyclic mechanical ** stresses, most materials fail at a stress considerably **lower than that required** to cause rupture in a single stress cycle.
fatigue
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performed to measure the **reduction in stiffness and strength of materials **under repeated loading and to determine the** total number of load cycles** to failure.
Fatigue Tests
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Various modes of fatigue testing in common use include
alternating tensile compressive stress cyclic flexural stress
206
measure the ability of a material to resist deformation in response to a sudden load
Impact Tests
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Four commonly used types of impact tests include
Charpy, Izod, drop-weight, and dynamic tear tests
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The benefits of conducting impact testing on materials include
- to determine a material’s toughness - establishing quality control standards - optimizing designs - picking appropriate materials for particular applications.
209
occurs if the material behaves elastically up to the point of failure
Brittle rupture
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occurs when the specimen is permanently distorted near the point of failure.
Ductile rupture
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The brittle point, or temperature at the onset of brittleness, is usually determined by subjecting a specimen to _____________________
impact in a standardized but empirical way.
212
commonly measured by tests in which a **pendulum with a massive striking edge** is allowed to **hit the specimen**. From the travel of the pendulum after breaking the specimen can be calculated the energy required to cause the break
Impact strength
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When plastics are used as films, particularly in packaging applications, their _______________ is an important property.
resistance to tearing
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a specimen is torn apart at a cut made by a sharp blade. Energy is provided by a falling pendulum, and the work done is measured by the residual energy of the pendulum
tear strength
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composite property combining concepts of resistance to penetration, scratching, marring, and so on
Hardness
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crucial characteristic that governs a material's resistance to abrasion, scratching, and other types of mechanical deformation
Polymer hardness
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It is an important consideration for choosing and designing polymers for a **range of applications**, including technical parts, consumer goods, and biomedical equipment
Hardness
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takes the form of a scratch test, in which the material is subjected to many scratches, usually from contact with an **abrasive wheel or a stream of falling abrasive material**
Abrasion Resistance
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defined as the temperature at which the resin flows under a given load on heating
Softening Temperature
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In measuring softening temperature 1) A polymer sample becomes molten and leaves a trail when moved across a ______________with moderate pressure (polymer melt or stick temperature tests;
hot metal surface
221
In measuring softening temperature 2) A polymer specimen fails in tension under its own weight
(zero-strength temperature test).
222
usually tested as the burning rate of a specified sample
Flammability
223
___________________ tendency of the material on the removal of an external flame is also important
self-extinguishing
224
A major determinant of the appearance of a transparent material is its _____________________
transmittance
225
the ratio of the intensities of light passing through and light incident on the specimen
transmittance
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The appearance of an opaque material is characterized by its ______________
reflectance
227
the ratio of the intensities of the reflected and the incident light
reflectance
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A _____________ substance is one that transmit part and reflects part of the light incident on it
translucent
229
______________________ and _____________________ may be measured as a function of the wavelength of light in a spectrophotometer
Transmittance and reflectance
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is the subjective sensation in the brain resulting from the perception of those aspects of the appearance of objects that result from the **spectral composition** of the **light reaching the eye.**
Color
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In commercial **hazemeters** only light deviating more than _____________ from the transmitted beam direction is considered haze.
2.5 degree
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The effect of __________ is to impart a cloudy or milky appearance to the sample
haze
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_____________ is defined as the state **permitting perception of objects **through or beyond the specimen.
Transparency
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of polymers refers to their** degree of clarity or opacity,** or how much they allow light to pass through them
Transparency
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Polymers can be made transparent by ________________________ their chemical structure, resulting in materials with varied levels of transparency.
incorporating additives or modifying
236
The transparency of polymers has numerous applications in industries such as __________________, where clarity is necessary for specific purposes.
packaging, textiles, and electronics
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refers to the ability of a polymer material to resist the flow of electrical current.
Resistivity
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important property of polymers used in electronic applications, such as in the production of **interconnected circuit components, conductive films, and insulators. **
Resistivity
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The resistivity of polymers can be modified through the ___________________________ through crosslinking or chain modification.
addition of conductive insulating fillers by altering the polymer structure
240
The value of the resistivity depends on factors such as the
type and concentration of the polymer the crosslink density the presence of defects
241
Both _______ and _____________ resistivity are important properties for applications of polymers as insulating materials.
volumesurface , volume
242
a measure of a material's ability to store electric charge.
Dielectric Constant
243
influenced by factors such as the type and structure of the polymer, as well as the presence of any** additional groups.**
Dielectric Constant
244
why Dielectric Constant needs to consider sa design?
it can affect performance and reliability
245
measure of its ability to sustain high-voltage differences without current breakdown.
Dielectric Strength
246
measure of the electrical strength of a material as an insulator
Dielectric Strength
247
affected by factors such as the type of polymer, its **molecular structure**, and the **presence of impurities. **
Dielectric Strength
248
________ dielectric strengths are typically desirable in capacitors
Higher
249
The surfaces of some polymers may become ______ and conduct current readily when exposed to an electrical discharge.
carbonized
250
ability of the plastic material to **resist the action of a high voltage electrical arc** and **resist the formation of a conducting path** along its surface under a given time.
Arc resistance
251
This property is important in applications such as
hightemperature dielectrics coatings insulation materials.
252
Polymer materials are chosen for their high arc resistance due to their ability to withstand ____________ and protect against _____________
high temperatures , electrical arcs
253
several forms of effects of solvents
solubility swelling including the absorption of water
254
specimen fails by **breaking when exposed to mechanical stress **in the presence of an organic **liquid** of an aqueous solution of a soap or other wetting agent
environmental stress cracking
255
specimen fails by the development of a **multitude of very small cracks** in the presence of an organic **liquid or its vapor**, **with or without the presence of mechanical stress**.
crazing
256
When polymers are exposed to solvents, they may become _____________ depending on the type of polymer and solvent
swollen or dissolved
257
The resistance of polymers to solvents can be influenced by factors such as the
polymer's structure solvent's strength temperature.
258
Polymers that are resistant to solvents are often used in applications where _______ and ________ are required, such as in clothing, tires, and electronics
strength , durability
259
**product of the solubility **of the gas or vapor in the polymer and its **diffusion coefficient**
permeability of a polymer to a gas or vapor
260
directly measured as the **rate of transfer of vapor** through **unit thickness** of the polymer in film form, **per unit area** and **pressure difference across the film.** (KT/AP)
Permeability
261
refers to the ability of a polymer material to allow certain gases or vapors to pass through it.
Vapor permeability
262
The vapor permeability of polymers can be influenced by factors such as the
molecular weight structure composition of the polymer presence of additives temperature humidity conditions
263
refers to the process of degradation of polymers, or large molecules, due to exposure to **external factors such as sunlight, temperature, and chemicals.**
Weathering
264
this can cause the polymer material to break down into smaller fragments, leading to changes in its physical and chemical properties.
Weathering
265
can have a significant impact on the performance and ***lifespan of polymer-based*** products, such as plastics, coatings, and rubber
Weathering